The present invention relates to a car-locating system for finding the position of a car in a vast place such as a parking lot, as well as for detecting an alarm from the car and for remote-controlling the door locking mechanism, air conditioner, etc. provided in the car.
When a person returns to a large parking lot, he sometimes cannot remember where he has parked his car and is, therefore, forced to walk around for a long time until he finds it. Similarly, on some occasions, he may ask his friend to retrieve the car from the parking lot, and his friend too usually has to spend much time in locating the car.
In order to locate a car parked in a vast place, a radar system may be used. Alternatively, as disclosed in Japanese Pat. Disclosure No. Sho 58-180350, a radio transmitter that transmits an ID code for as long as a car is parked, is provided in a car. The person looking for the car uses a portable radio receiver to detect the ID code and the direction in which this code is transmitted, thereby locating the car.
A radar system is very complex and too expensive to be used for this purpose. Moreover, even if used to locate a parked car, the system cannot distinguish it from the other cars parked in the same place. When a radio transmitter and a radio receiver are used, two problems arise. First, since the transmitter must emit the ID code for the duration the car is parked, it quickly uses up the car's battery. Secondly, when many ID codes are transmitted from other cars parked in the same parking lot, the receiver may pick up a wrong ID code, inevitably guiding its holder to the wrong parking space.